help with "symbol lookup error" message

Special_K has asked for the wisdom of the Perl Monks concerning the following question:

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Re: help with "symbol lookup error" message by Corion (Patriarch) on Jan 26, 2023 at 18:48 UTC
Maybe some module that File::Copy loads in turn tries to load List::Util. Most likely, the root cause is you have mixed Perl versions and the modules below `/home/user_foo/perl_modules` were compiled for a different version of Perl / with a different C compiler / with different Configure settings than what you have now.	[reply] [d/l]
Re: help with "symbol lookup error" message by syphilis (Archbishop) on Jan 27, 2023 at 01:38 UTC
The error references the List::Util module, but doesn't occur unless I add the "use File::Copy", ... The odd thing there is that List::Util is being referenced, but I don't see how List::Util (which is quite separate from List::MoreUtils) gets loaded. If your account of what's happening is accurate, then the only explanation I can think of is that, on your system, using File::Copy leads to the loading of List::Util (either by "`use`" or "`require`"), and the incompatible List::Util intalled in `/home/user_foo/perl_modules/lib/perl5` is the one that gets found. On my system, `use File::Copy` does not lead to List::Util being loaded - but File::Copy probably does some things differently on different systems. If you want to check which modules have been loaded by your script (and where they were found), just add the following line at the end of your script: `for(keys %INC) { print "$_: $INC{$_}\n" };` [download] If placed at the end of the script, that will not only tell you the modules that were loaded by "use", but also any modules that were subsequently loaded via "require" during the running of your script. (That's assuming, of course, that the script runs to completion ;-) Cheers, Rob	[reply] [d/l] [select]
Re^2: help with "symbol lookup error" message by hippo (Bishop) on Jan 27, 2023 at 10:36 UTC
(That's assuming, of course, that the script runs to completion ;-) Since that's the problem facing Special_K perhaps using a coderef in @INC will be a more useful strategy in this instance^. `#!/usr/bin/env perl use strict; use warnings; BEGIN { unshift @INC, sub { warn "Loading $_[1]\n"; 0; }; } use File::Copy;` [download] When I run this (with File::Copy 2.35 on perl 5.34.0 on Linux) the result is: `Loading File/Copy.pm Loading File/Spec.pm Loading File/Spec/Unix.pm Loading Cwd.pm Loading Exporter.pm Loading XSLoader.pm Loading constant.pm Loading warnings/register.pm Loading Config.pm Loading Time/HiRes.pm Loading Exporter/Heavy.pm Loading Scalar/Util.pm Loading List/Util.pm Loading overload.pm Loading overloading.pm` [download] So List::Util is in there on my platform right enough. ^ I'm sure there's a module for this but I can neither remember nor find it just now. 🦛	[reply] [d/l] [select]
Re^3: help with "symbol lookup error" message by syphilis (Archbishop) on Jan 27, 2023 at 12:11 UTC
So List::Util is in there on my platform right enough Aaah ... cool. AFAICS, this absurd dependency is not present in perl-5.36.0 - on both Windows and freebsd-12.0. On Windows (perl-5.36.0), your script outputs: `Loading File/Copy.pm Loading builtin.pm Loading overload.pm Loading overloading.pm Loading warnings/register.pm Loading File/Spec.pm Loading File/Spec/Win32.pm Loading Cwd.pm Loading Exporter.pm Loading XSLoader.pm Loading File/Spec/Unix.pm Loading constant.pm Loading Config.pm Loading Time/HiRes.pm Loading Carp.pm` [download] On freebsd (5.36.0), it's exactly the same - except that Carp.pm and File/Spec/Win32.pm are not loaded, and Exporter/Heavy.pm is loaded. I'm sure there's a module for this but I can neither remember nor find it just now I reckon the code you posted is much clearer for not having loaded that module (whatever it is ;-) Cheers, Rob	[reply] [d/l]
Re^4: help with "symbol lookup error" message by hippo (Bishop) on Jan 27, 2023 at 12:39 UTC
Re^5: help with "symbol lookup error" message by syphilis (Archbishop) on Jan 27, 2023 at 13:18 UTC
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Re^3: help with "symbol lookup error" message by Special_K (Monk) on Jan 28, 2023 at 18:01 UTC
> When I run this (with File::Copy 2.35 on perl 5.34.0 on Linux) the result is: Is File::Copy versioned separately from Perl itself? When I look at the CPAN page it looks like File::Copy shares the version number of the perl distribution it is included with (unless I'm interpreting the webpage wrong): https://metacpan.org/pod/File::Copy So what's happening is that in perl 5.34.0 and earlier, a module that is included with Perl by default (File::Copy) is calling a module that is not (List::Util)? And then perl 5.36 removed this dependency?	[reply]
Re^4: help with "symbol lookup error" message by hippo (Bishop) on Feb 02, 2023 at 11:58 UTC
Re^5: help with "symbol lookup error" message by Special_K (Monk) on Feb 03, 2023 at 20:28 UTC
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Re^4: help with "symbol lookup error" message by kcott (Archbishop) on Feb 04, 2023 at 05:11 UTC
Re^3: help with "symbol lookup error" message by Special_K (Monk) on Jan 27, 2023 at 23:12 UTC
This question is tangential to my main issue, but since I've never seen the code before, could you please explain what exactly this is doing: `unshift @INC, sub { warn "Loading $_[1]\n"; 0; };` [download] It looks like it's creating an array of subroutines, where each subroutine just prints the same element (1). The 0 I'm guessing is just a required return value? I must be missing something here.	[reply] [d/l]
Re^4: help with "symbol lookup error" message by choroba (Cardinal) on Jan 27, 2023 at 23:23 UTC
Re^4: help with "symbol lookup error" message by Anonymous Monk on Jan 28, 2023 at 06:23 UTC
Re^4: help with "symbol lookup error" message by Anonymous Monk on Jan 28, 2023 at 06:04 UTC
Re^3: help with "symbol lookup error" message by Anonymous Monk on Feb 02, 2023 at 11:23 UTC
#!/usr/bin/perl use strict; use warnings; BEGIN { unshift @INC, sub { warn "Loading $_[1]\n"; push @ARGV, $_[1] } } use File::Copy; print "$^V\n"; print "$_\n" for sort {lc $a cmp lc $b} @ARGV; __END__ v5.18.2 Config.pm Exporter.pm File/Copy.pm File/Spec.pm File/Spec/Unix.pm List/Util.pm overload.pm overloading.pm Scalar/Util.pm vars.pm warnings/register.pm XSLoader.pm > constant.pm > DynaLoader.pm v5.20.3 Config.pm constant.pm DynaLoader.pm Exporter.pm File/Copy.pm File/Spec.pm File/Spec/Unix.pm List/Util.pm overload.pm overloading.pm Scalar/Util.pm vars.pm warnings/register.pm XSLoader.pm < DynaLoader.pm > Cwd.pm v5.26.2 Config.pm constant.pm Cwd.pm Exporter.pm File/Copy.pm File/Spec.pm File/Spec/Unix.pm List/Util.pm overload.pm overloading.pm Scalar/Util.pm vars.pm warnings/register.pm XSLoader.pm < vars.pm > Exporter/Heavy.pm > Time/HiRes.pm v5.28.0 Config.pm constant.pm Cwd.pm Exporter.pm Exporter/Heavy.pm File/Copy.pm File/Spec.pm File/Spec/Unix.pm List/Util.pm overload.pm overloading.pm Scalar/Util.pm Time/HiRes.pm warnings/register.pm XSLoader.pm < List/Util.pm < Scalar/Util.pm > builtin.pm v5.36.0 builtin.pm Config.pm constant.pm Cwd.pm Exporter.pm Exporter/Heavy.pm File/Copy.pm File/Spec.pm File/Spec/Unix.pm overload.pm overloading.pm Time/HiRes.pm warnings/register.pm XSLoader.pm [download]	[reply] [d/l]
Re^3: help with "symbol lookup error" message by Special_K (Monk) on Feb 03, 2023 at 20:41 UTC
Is it possible to modify this code to see where the modules are being called from? For example, to see that List/Util.pm is being called by File/Copy.pm?	[reply]
Re^4: help with "symbol lookup error" message by hippo (Bishop) on Feb 03, 2023 at 23:13 UTC
Re^2: help with "symbol lookup error" message by xiaoyafeng (Deacon) on Feb 02, 2023 at 04:17 UTC
If you want to check which modules have been loaded by your script (and where they were found), just add the following line at the end of your script: for(keys %INC) { print "$_: $INC{$_}\n" }; I recommend using perldebug, which is more clear and simple: perl -MFile::copy -de0 DB<1> M 'Carp.pm' => '1.50 from C:/Strawberry/perl/lib/Carp.pm' 'Config.pm' => '5.032001 from C:/Strawberry/perl/lib/Config.pm' 'Config_git.pl' => 'C:/Strawberry/perl/lib/Config_git.pl' 'Config_heavy.pl' => 'C:/Strawberry/perl/lib/Config_heavy.pl' 'Cwd.pm' => '3.78 from C:/Strawberry/perl/lib/Cwd.pm' 'DynaLoader.pm' => '1.47_01 from C:/Strawberry/perl/lib/DynaLoader.pm' 'Exporter.pm' => '5.74 from C:/Strawberry/perl/lib/Exporter.pm' 'File/Spec.pm' => '3.78 from C:/Strawberry/perl/lib/File/Spec.pm' 'File/Spec/Unix.pm' => '3.78 from C:/Strawberry/perl/lib/File/Spec/Uni +x.pm' 'File/Spec/Win32.pm' => '3.79 from C:/Strawberry/perl/lib/File/Spec/Wi +n32.pm' 'File/copy.pm' => 'C:/Strawberry/perl/lib/File/copy.pm' 'IO.pm' => '1.45 from C:/Strawberry/perl/lib/IO.pm' 'IO/Handle.pm' => '1.45 from C:/Strawberry/perl/lib/IO/Handle.pm' 'List/Util.pm' => '1.55 from C:/Strawberry/perl/lib/List/Util.pm' 'Scalar/Util.pm' => '1.55 from C:/Strawberry/perl/lib/Scalar/Util.pm' 'SelectSaver.pm' => '1.02 from C:/Strawberry/perl/lib/SelectSaver.pm' 'SelfLoader.pm' => '1.26 from C:/Strawberry/perl/lib/SelfLoader.pm' 'Symbol.pm' => '1.08 from C:/Strawberry/perl/lib/Symbol.pm' 'Term/Cap.pm' => '1.17 from C:/Strawberry/perl/lib/Term/Cap.pm' 'Term/ReadKey.pm' => '2.38 from C:/Strawberry/perl/vendor/lib/Term/Rea +dKey.pm' 'Term/ReadLine.pm' => '1.17 from C:/Strawberry/perl/lib/Term/ReadLine. +pm' 'Term/ReadLine/Perl.pm' => '1.0303 from C:/Strawberry/perl/vendor/lib/ +Term/ReadLine/Perl.pm' 'Term/ReadLine/readline.pm' => '1.0303 from C:/Strawberry/perl/vendor/ +lib/Term/ReadLine/readline.pm' 'Time/HiRes.pm' => '1.9764 from C:/Strawberry/perl/lib/Time/HiRes.pm' 'Win32.pm' => '0.54 from C:/Strawberry/perl/lib/Win32.pm' 'XSLoader.pm' => '0.30 from C:/Strawberry/perl/lib/XSLoader.pm' 'constant.pm' => '1.33 from C:/Strawberry/perl/lib/constant.pm' 'feature.pm' => '1.58 from C:/Strawberry/perl/lib/feature.pm' 'overload.pm' => '1.31 from C:/Strawberry/perl/lib/overload.pm' 'overloading.pm' => '0.02 from C:/Strawberry/perl/lib/overloading.pm' 'perl5db.pl' => '1.57 from C:/Strawberry/perl/lib/perl5db.pl' 'strict.pm' => '1.11 from C:/Strawberry/perl/lib/strict.pm' 'vars.pm' => '1.05 from C:/Strawberry/perl/lib/vars.pm' 'warnings.pm' => '1.47 from C:/Strawberry/perl/lib/warnings.pm' 'warnings/register.pm' => '1.04 from C:/Strawberry/perl/lib/warnings/r +egister.pm' [download] I am trying to improve my English skills, if you see a mistake please feel free to reply or /msg me a correction	[reply] [d/l]
Re: help with "symbol lookup error" message by LanX (Saint) on Jan 26, 2023 at 19:47 UTC
that's a continuation of "symbol lookup error" message help ,right? Cheers Rolf _{(addicted to the 𐍀𐌴𐍂𐌻 Programming Language :) Wikisyntax for the Monastery}	[reply]
Re^2: help with "symbol lookup error" message by Special_K (Monk) on Jan 27, 2023 at 23:13 UTC
Correct, this a new issue related to the one described in the other thread. I wasn't sure if it made more sense to create a new thread or start a different discussion in the other one (although they are obviously related).	[reply]


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